linux-kernel - Re: [PATCH RT v2] Fix a lockup in wait_for

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Message-ID: <20190702114028.GE5041@minyard.net>
Date:   Tue, 2 Jul 2019 06:40:28 -0500
From:   Corey Minyard <cminyard@...sta.com>
To:     Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Cc:     Kurt Kanzenbach <kurt.kanzenbach@...utronix.de>,
        Steven Rostedt <rostedt@...dmis.org>,
        Corey Minyard <minyard@....org>,
        linux-rt-users@...r.kernel.org, linux-kernel@...r.kernel.org,
        Peter Zijlstra <peterz@...radead.org>, tglx@...utronix.de
Subject: Re: [PATCH RT v2] Fix a lockup in wait_for_completion() and friends

On Tue, Jul 02, 2019 at 10:35:36AM +0200, Sebastian Andrzej Siewior wrote:
> On 2019-07-02 09:04:18 [+0200], Kurt Kanzenbach wrote:
> > > In fact, my system doesn't boot with this commit in 5.0-rt.
> > >
> > > If I revert 90e1b18eba2ae4a729 ("swait: Delete the task from after a
> > > wakeup occured") the machine boots again.
> > >
> > > Sebastian, I think that's a bad commit, please revert it.
> > 
> > I'm having the same problem on a Cyclone V based ARM board. Reverting
> > this commit solves the boot issue for me as well.
> 
> Okay. So the original Corey fix as in v5.0.14-rt9 works for everyone.
> Peter's version as I picked it up for v5.0.21-rt14 is causing problems
> for two persons now.
> 
> I'm leaning towards reverting it back to old version for now…

Just to avoid confusion... it wasn't my patch 1921ea799b7dc56
(sched/completion: Fix a lockup in wait_for_completion()) that caused
the issue, nor was it Peter's version of it.  Instead, it was the patch
mentioned above, 90e1b18eba2ae4a729 ("swait: Delete the task from after a
wakeup occured"), which came from someone else.  I can verify by visual
inspection that that patch is broken and it should definitely be removed.
Just don't want someone to be confused and remove the wrong patch.

-corey


> 
> > Thanks,
> > Kurt
> 
> Sebastian